Have you been browsing for doors? Then you’ve probably come across the term ‘u-value’. You think that it somehow relates to energy efficiency, but what exactly does it mean?
You’re correct in assuming that u-values refer to the energy efficiency of doors and also windows and walls. In particular, they’re used to quantify thermal efficiency.
Besides looks, security, and safety, thermal efficiency is an important attribute often overlooked. Thermally efficient doors are better at retaining the warmth inside your home. That means that the door helps keep your energy bills low since your heater doesn’t have to work as much.
It’s an investment that’ll pay for itself and then some!
In this article, you’ll learn why looking at the u-value can guide you on your quest to find the perfect door. Let’s get to it.
What Are U-Values?
Let’s talk about what the u-value is and how it ties into thermal efficiency.
The u-value or u-factor measures the rate of heat transfer. It’s how fast any given system can conduct heat from one side to the other side. Therefore, you want a lower u-value if you’re aiming for energy efficiency.
It’s measured in watts per square meter Kelvin (W/m2K). No need to bother with how it’s calculated if you don’t want to, but if you’re curious, you can check out this site. The only thing you should remember is that for u-values, lower is better.
How Is It Different From R-Value?
Another number that pops up when you’re looking at energy performance ratings is the r-value. The “R” here stands for “resistance”. It refers to how much resistance a material offers against heat flow.
In other words, it’s a measurement of the insulation of particular construction materials. In this case, the higher the r-value, the better the door insulation.
In effect, the r-value is the inverse of the u-value.
One important difference is that the r-value only applies to specific materials. The u-value can be used to represent the energy efficiency of systems where multiple materials are used. This is important because some of the best performing doors in terms of energy efficiency are composite doors.
What’s a Good U-Value Number?
You now know that when looking at the u-value, lower is better. How low is low enough?
According to the Irish Building Regulations of 2019, the maximum elemental u-value for external doors is 3.0. However, you’re required to have the maximum area-weighted average u-value of 1.4 for all your exterior doors, windows, and roof lights.
In general, any u-value below 1 is excellent. You usually see this in triple-glazed doors with a thermal upgrade. For reference, a solid oak door would have a u-value of around 3, while an insulated cavity wall has a u-value of about 0.5.
What Are My Options for an Energy-Efficient Door?
If you’re looking for doors that won’t waste energy, PVC and composite doors are your best bets.
The core materials of the panel of PVC doors are bonded together to enhance insulation. And as mentioned before, composite doors have some of the best u-values. That’s because you can make a composite door with materials that have first-rate insulation.
We offer PVC, composite, and other energy-efficient doors here at Weathermaster Kerry. When you shop from us, you’re assured of quality and a lower utility bill each month. Contact us today!